add support for m68k 80-bit long double variant

since x86 and m68k are the only archs with 80-bit long double and each
has mandatory endianness, select the variant via endianness.
differences are minor: apparently just byte order and representation
of infinities. the m68k format is not well-documented anywhere I could
find, so if other differences are found they may require additional
changes later.

diff --git a/src/internal/libm.h b/src/internal/libm.h
index df8641116af2ee442525828bfc27bc2de75ee508..a2505f7ece62ba2cc494201f234c457c7b37ed4b 100644 (file)
--- a/src/internal/libm.h
+++ b/src/internal/libm.h
@@ -28,6 +28,17 @@ union ldshape {
                uint16_t se;
        } i;
 };
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384 && __BYTE_ORDER == __BIG_ENDIAN
+/* This is the m68k variant of 80-bit long double, and this definition only works
+ * on archs where the alignment requirement of uint64_t is <= 4. */
+union ldshape {
+       long double f;
+       struct {
+               uint16_t se;
+               uint16_t pad;
+               uint64_t m;
+       } i;
+};
 #elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384 && __BYTE_ORDER == __LITTLE_ENDIAN
 union ldshape {
        long double f;

diff --git a/src/math/__fpclassifyl.c b/src/math/__fpclassifyl.c
index 481c0b949974ad43a59e95846bf9fb83ff5cbf23..e41781b689af7f7db420fc437cc4a72e4dd00c33 100644 (file)
--- a/src/math/__fpclassifyl.c
+++ b/src/math/__fpclassifyl.c
@@ -13,10 +13,18 @@ int __fpclassifyl(long double x)
        int msb = u.i.m>>63;
        if (!e && !msb)
                return u.i.m ? FP_SUBNORMAL : FP_ZERO;
+       if (e == 0x7fff) {
+               /* The x86 variant of 80-bit extended precision only admits
+                * one representation of each infinity, with the mantissa msb
+                * necessarily set. The version with it clear is invalid/nan.
+                * The m68k variant, however, allows either, and tooling uses
+                * the version with it clear. */
+               if (__BYTE_ORDER == __LITTLE_ENDIAN && !msb)
+                       return FP_NAN;
+               return u.i.m << 1 ? FP_NAN : FP_INFINITE;
+       }
        if (!msb)
                return FP_NAN;
-       if (e == 0x7fff)
-               return u.i.m << 1 ? FP_NAN : FP_INFINITE;
        return FP_NORMAL;
 }
 #elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384